Table of Contents
- Introduction
- Identifying the Top and Bottom of a Begonia Tuber
- Why Orientation Matters for Begonias
- What to Do if the Tuber Is Flat
- Choosing the Right Soil and Container
- Starting Begonias Indoors vs. Outdoors
- Watering Rules for Newly Planted Tubers
- Lighting and Location for Best Success
- Exploring Different Begonia Varieties
- Maintaining Your Begonias Throughout the Season
- Preparing for the End of the Season
- Conclusion
- FAQ
Introduction
Tuberous begonias are the stars of the summer shade garden, offering lush foliage and brilliant flowers that look like roses or camellias. Watching these unique tuberous begonias grow from a simple brown tuber into a cascading display of color is one of the most rewarding experiences a gardener can have. Because begonias thrive in areas where many other flowers struggle, they are a favorite for porch containers, hanging baskets, and shaded garden beds.
At Longfield Gardens, we want to help you feel confident from the moment you open your shipment of tubers. While they might look a little unusual at first glance, begonia bulbs are very easy to handle once you know what to look for. The most common question we receive from new growers is about orientation: which side is the top and which is the bottom?
This guide will help you identify the correct way to plant your begonia tubers so they can sprout quickly and grow into healthy, vibrant plants. We will cover the anatomy of the tuber, the best planting depth, and how to give your begonias the best start whether you are planting them in a pot or directly in the ground. Knowing which way up to plant your begonia bulbs ensures your garden season starts on the right foot. For more growing advice, see our Tips for Growing Tuberous Begonias.
Identifying the Top and Bottom of a Begonia Tuber
When you first hold a begonia tuber, you will notice it doesn't look like a typical pointed tulip or daffodil bulb. Instead, it looks more like a dark, hairy potato or a thick, woody coin. These tubers are actually swollen underground stems that store energy for the plant. Because they lack a distinct "point," identifying the top requires a closer look at the shape and texture.
The most reliable way to tell which side is the top is to look for the "bowl." Tuberous begonias have a concave side and a convex side. The concave side looks like a shallow dish or a bowl with a slight hollow in the center. This hollow side is the top. The convex side is rounded, like the bottom of a bowl or a dome, and this side should face down into the soil.
If you look closely at the hollow side, you may see small, pinkish or white bumps. These are called "eyes," much like the eyes on a potato. These eyes are the growth points where the stems and leaves will eventually emerge. On the rounded bottom side, you will usually see a rougher texture where old roots were once attached. Even if you don't see any sprouts yet, placing the hollow side facing up toward the sky is the golden rule for begonias.
Why Orientation Matters for Begonias
You might wonder if a plant can figure out which way to grow even if it is planted upside down. While plants do have a natural sense of gravity, planting a begonia tuber correctly makes a significant difference in its early health. When the hollow side faces up, the sprouts have a direct and easy path to the surface. This allows the plant to begin photosynthesis sooner, which provides it with more energy to grow.
If a tuber is planted upside down, the stems must grow downward first and then curve around the tuber to reach the light. This extra effort uses up the stored energy inside the bulb and can delay the appearance of the plant by several weeks. In some cases, if the soil is very heavy or wet, an upside-down tuber may struggle to reach the surface at all.
By taking a moment to ensure the "bowl" is facing up, you are giving the plant its best chance at a vigorous start. It helps the roots on the bottom establish themselves quickly in the soil while the sprouts on top head straight for the sun. This simple step is the foundation of a successful growing season.
Key Takeaway: The Quick Identification Rule
- Hollow/Dipped Side: This is the top. It should face UP.
- Rounded/Domed Side: This is the bottom. It should face DOWN.
- Look for "Eyes": Small pink or white bumps will always be on the hollow top side.
What to Do if the Tuber Is Flat
Sometimes, a begonia tuber may appear quite flat, making it harder to distinguish the hollow side from the rounded side. This can happen with certain varieties or smaller tubers. If you encounter a tuber that doesn't have a clear "bowl" shape, don't worry. There are still a few tricks to find the right direction.
First, look for remnants of the previous year's growth. You might see a small, dried-up circular scar where the main stem was attached. This scar will always be on the top of the tuber. You can also look for any fine, hair-like dried roots. While roots can sometimes grow from the sides, they are most prevalent on the bottom and edges of the rounded side.
If you still aren't sure, the safest option is to plant the tuber on its side. Begonias are remarkably resilient. When planted on its side, the sprouts will naturally grow toward the light and the roots will grow toward the moisture. This is a great "insurance" method for those few tubers that seem to defy the standard bowl shape. For a broader overview, see our All About Begonias guide.
Choosing the Right Soil and Container
Once you know which way is up, the next step is providing the right environment. Begonias are not very picky, but they do have one firm requirement: excellent drainage. "Drainage" simply refers to how quickly water moves through the soil. Begonia tubers are fleshy and store a lot of water, which makes them susceptible to rot if they sit in soggy, waterlogged soil for too long.
For container gardening, always use a high-quality potting mix rather than garden soil. Potting mixes are designed to be light and airy, often containing peat moss, perlite, or vermiculite to help with drainage. Ensure your pot has at least one drainage hole at the bottom. We recommend choosing a container that is at least 6 to 8 inches deep to allow the root system plenty of room to expand. If you plan to use hanging baskets, see our Hanging Begonias collection.
If you are planting in the ground, look for a spot where the soil is loose and rich. If your soil is heavy clay, you can improve the drainage by mixing in some organic matter like compost or shredded bark. A simple test is to watch the area after a rainstorm. If the water disappears quickly, it is a great spot for begonias. If puddles remain for hours, you might want to consider a raised bed or a container instead.
Planting Depth and Spacing
Getting the depth right is just as important as the orientation. Begonias do not like to be buried deep in the earth. In fact, they prefer to be quite close to the surface. For most varieties, the top of the tuber should be covered by only about an inch of soil.
When planting, follow these simple steps:
- Dig a shallow hole or indentation in the soil.
- Place the tuber with the hollow side facing up.
- Cover the tuber with about 1 inch of loose soil.
- Gently pat the soil down to ensure good contact, but do not pack it tightly.
Spacing depends on the variety of begonia you are growing. Upright Double Begonias, such as the Double Begonias we offer at Longfield Gardens, usually need about 8 to 12 inches of space between them. If you are planting Pendula or hanging basket varieties, you can place them a bit closer together—about 6 inches apart—to create a fuller, more lush look in your containers.
Starting Begonias Indoors vs. Outdoors
Because begonias are tropical plants, they love warmth and are very sensitive to frost. Depending on where you live, you have two options for when to plant. If you're not sure how your climate affects planting time, our Hardiness Zone Map can help.
The Indoor Head Start
Most gardeners prefer to start their begonia tubers indoors about 6 to 8 weeks before the last expected frost in their area. This "head start" is beneficial because begonias can be slow to wake up. By starting them inside in late winter or early spring, you ensure they are already growing and perhaps even blooming by the time the weather is warm enough to move them outside.
To start indoors, place your tubers in small pots or a shallow tray with potting mix. Keep them in a warm spot (around 70°F) with indirect light. You don't need bright sun yet; the warmth is what tells the tuber it is time to grow. Once you see green leaves poking through the soil, move them to a brighter window.
Planting Directly Outdoors
If you live in a warm climate or prefer to wait, you can plant begonias directly in the garden once the soil has warmed up and all danger of frost has passed. The soil temperature should be at least 60°F. While this method is easier, keep in mind that it may take several weeks for the tubers to sprout and even longer for them to flower. They will eventually catch up, but your blooming season will be shorter than if you had started them indoors.
What to Do Next: Your Planting Checklist
- Check the weather: Ensure your indoor space is warm or the outdoor frost date has passed.
- Select your site: Choose a spot with partial shade and well-draining soil.
- Identify the top: Find the hollow "bowl" side of the tuber.
- Set the depth: Plant the tuber hollow-side up, 1 inch below the soil surface.
- Water lightly: Provide just enough moisture to settle the soil.
Watering Rules for Newly Planted Tubers
Watering is the area where most beginners make mistakes. When a begonia tuber is first planted and has no leaves, it has no way to "use" a lot of water. If the soil is kept too wet during this dormant stage, the tuber may rot before it ever has a chance to sprout.
The rule for newly planted begonias is to water sparingly. After you first plant the tuber, give it a light watering to settle the soil around it. Then, wait. Don't water again until the top inch of soil feels dry to the touch. Once you see green sprouts emerging from the soil, you can gradually increase the frequency of watering.
As the plant grows and develops more leaves, it will naturally need more moisture. Begonias like to stay consistently damp but never "wet." A good technique is to water deeply until water runs out the bottom of the pot, and then let the soil surface dry out slightly before watering again. This encourages the roots to grow deep into the container.
Lighting and Location for Best Success
While begonias are famous for being shade plants, they still need some light to produce their spectacular flowers. The term "shade" can be confusing. In gardening, most begonias prefer "dappled shade" or "filtered light." This means they love the light that comes through the leaves of a tall tree or the bright, indirect light on a north-facing porch. For more ideas on shade-loving summer flowers, see our Summer Bulbs for Shady Gardens.
Avoid placing your begonias in the harsh, direct afternoon sun. The intense heat can scorch their tender leaves and cause the flowers to wilt. Morning sun is usually fine because it is cooler. If you notice your begonia stems are becoming very long and "leggy" with few flowers, they might be asking for a bit more light. Conversely, if the leaves look brown and crispy on the edges, they may be getting too much sun.
Finding the right balance is easy. A spot that feels bright enough to read a book comfortably, but doesn't have hot sun hitting the plant directly, is usually perfect. At Longfield Gardens, we have found that begonias in these conditions produce the largest blooms and the most vibrant colors.
Exploring Different Begonia Varieties
One of the joys of growing begonias is the incredible variety available. Each type has the same basic planting requirements, but their growth habits vary. Knowing which type you have can help you decide where to plant it.
Double Begonias
These are the classics. They produce large, multi-petaled flowers that look like roses, and Begonia Upright Double Roseform Pink is a great example. They grow on upright stems and are perfect for garden borders or patio pots. When planting these, ensure the hollow side is facing up to support those heavy, beautiful flower heads.
Pendula (Hanging Basket) Begonias
As the name suggests, these begonias have a cascading habit. Instead of growing straight up, the stems drape over the sides of the container. Begonia Hanging Golden Balcony is a classic choice for hanging baskets or window boxes. Because they will be viewed from below, you want to make sure they are healthy and well-watered to keep the stems flexible and full of blooms.
Fimbriata Begonias
These unique begonias have ruffled, fringed edges on their petals, giving them a carnation-like appearance. They add a wonderful texture to the garden. Like the others, they grow from a central tuber and require the same "bowl-side-up" orientation to flourish.
Picotee Begonias
Picotee varieties feature petals with a contrasting color on the edges. They are stunning when viewed up close in containers on a porch or table. Because the detail is so fine, planting them at eye level in pots allows you to appreciate the intricate color patterns. A variety like Begonia Upright Double Picotee White makes that detail easy to enjoy.
Maintaining Your Begonias Throughout the Season
Once your begonias are planted correctly and have started growing, maintenance is very straightforward. These plants are relatively low-maintenance, but a few simple tasks will keep them blooming until the first frost of autumn.
Deadheading
"Deadheading" is just a fancy word for removing faded flowers. When a bloom starts to wilt or turn brown, gently pinch it off at the base of its small stem. This prevents the plant from putting energy into producing seeds and encourages it to keep producing new flower buds instead. It also keeps your plants looking tidy and fresh.
Fertilizing
Begonias are heavy feeders because they produce so many flowers over a long season. Once your plants have several sets of leaves, you can begin using a balanced, water-soluble fertilizer. Following the instructions on the product label is important; usually, a feeding every two weeks is sufficient. This provides the nutrients the plant needs to sustain its growth and keep those colors bright.
Managing Pests and Airflow
Begonias are generally healthy, but they do appreciate good airflow. If the plants are crowded too closely together, they can sometimes develop powdery mildew—a white, dusty-looking fungus on the leaves. To prevent this, simply give your plants enough space so air can circulate around them. If you see any damaged or yellowing leaves, remove them promptly to keep the plant healthy.
Preparing for the End of the Season
As tropical plants, begonias will not survive a freezing winter in most parts of the United States. However, the tubers themselves can be saved and replanted year after year. This is one of the best things about begonias—they are a long-term investment for your garden.
When the weather begins to cool in the fall and the leaves start to turn yellow, stop fertilizing and reduce your watering. This signals to the plant that it is time to go dormant. After the first light frost kills the foliage, you can lift the tubers out of the soil.
Gently shake off the excess dirt and let the tubers dry in a cool, protected spot for a few days. Once dry, store them in a box with some peat moss or shredded paper in a cool, dark place (like a basement) that stays above freezing. Next spring, you can pull them out, find that "bowl" side again, and start the cycle all over.
Conclusion
Planting begonia tubers is a simple process that leads to a summer full of spectacular color. By remembering to place the hollow side facing up and the rounded side facing down, you remove the biggest hurdle to success. Whether you start them early indoors for a lush spring display or plant them directly in your summer garden beds, these versatile plants are sure to impress.
At Longfield Gardens, we take pride in providing high-quality tubers that are ready to perform, and our 100% guarantee is part of that promise. Gardening should be a relaxing and joyful hobby, and begonias are the perfect plant to prove how achievable a beautiful yard can be. With just an inch of soil, a little bit of shade, and the right orientation, you are well on your way to a stunning display.
Your Encouraging Next Step Now that you know exactly which way is up, take a look at your garden and identify a shaded spot that needs a splash of color. Whether it's a porch, a balcony, or the space under an old oak tree, there is always room for a few begonias. Ready to get started? Visit us at Longfield Gardens to pick out your favorite colors and varieties for the coming season, and review our Shipping Information when you're ready to order.
FAQ
What happens if I plant my begonia tuber completely upside down?
If a tuber is planted upside down, it isn't necessarily a disaster. The plant will still try to grow, but the stems will have to travel a much longer path to reach the surface. This can lead to a very late start for your flowers and might result in a weaker plant initially. If you realize your mistake within a week or two of planting, you can gently dig it up and flip it over.
Do I need to soak begonia tubers before planting?
Soaking is not strictly necessary for begonia tubers, but some gardeners like to do it to "wake them up." If you choose to soak them, only leave them in room-temperature water for about an hour. Be very careful not to leave them in water for too long, as this can lead to rot before they even get into the soil. Most of the time, planting them in moist soil is more than enough to trigger growth.
How long does it take for begonia tubers to sprout?
Begonias are notoriously slow starters. It can take anywhere from 3 to 6 weeks to see the first green shoots appearing above the soil. This timeline depends heavily on the temperature; they will sprout much faster in a warm room (70°F) than in a cool one. Patience is key when it comes to begonias, but once they start growing, they develop very quickly.
Can I grow begonias in full sun if I water them more?
Most tuberous begonias will struggle in full sun, even with extra water. The intense heat can physically damage the leaves and cause the flowers to drop prematurely. While there are some newer varieties bred for more sun tolerance, the classic tuberous begonias we carry perform best in partial to full shade. If your garden is very sunny, consider placing them in a spot that gets sun only in the very early morning.